The present application relates to III-V compound semiconductor field effect transistors (FETs), and more particularly to III-V compound semiconductor FETs having self-aligned source/drain contacts with low contact resistance.
III-V compound semiconductor materials with high electron mobility have been explored as a new channel material for n-type metal oxide semiconductor FETs (nMOSFETs). For III-V compound semiconductor-based nFETs, low resistance source/drain contacts are critical for the performance and reliability of the FETs. These low resistance source/drain contacts are traditionally done with a Ti/Pd/Au metallurgy. However, this metallurgy has poor thermal stability because Au starts to diffuse into junctions at modest processing temperatures, e.g. greater than 300° C., causing degradation of the gate metal and device shorts. Thus, the prior art metallurgy is not compatible with any high temperature process step following the contact formation. Therefore, there remains a need to develop low resistance and stable source/drain contacts for III-V compound semiconductor-based FETs.